Purpose :
Data on scotopic function throughout the macula in eyes with intermediate AMD (iAMD) remains limited. This study evaluated retinotopic macular scotopic function in healthy controls and iAMD eyes with and without reticular pseudodrusen (RPD).

Methods :
Scotopic thresholds for the 505 nm (cyan) and 620 nm (red) stimuli were obtained from 13 normal control, 15 iAMD without RPD and 15 iAMD with RPD participants, using a Medmont dark-adapted chromatic perimeter. Measurements were performed in one eye after 20 and 30 minutes of dark adaptation (DA) and the test grid consisted of 24 test locations spaced within the central 24°. The average point-wise sensitivity (PWS) for each stimulus and the sensitivity difference (cyan threshold - red threshold, for assessing rod function) were compared between the study groups.

Results :
The average PWS in iAMD eyes without RPD for 550 nm (51.3 ± 6.7 dB, p = 1.00) and 620 nm stimuli (29.9± 4.8 dB, p = 1.00) were similar to that of the control eyes (51.6 ± 6.3 dB for 550 nm and 30.0 ± 5.3 dB for 620 nm). However, the average PWS in iAMD eye with RPD for the 550 nm and 620 nm stimulus were significantly reduced in the central 8° compared to control eyes (48.6 ± 9.7 dB, p < 0.001 and 28.7± 6.4 dB, p = 0.04, respectively). The sensitivity difference at 20 and 30 minutes DA of iAMD eyes without RPD was similar to that of the controls at all test points (p ≥ 0.68). In iAMD eyes with RPD, the sensitivity difference at 20 and 30 minutes DA was significantly smaller than that of the controls, but only at test locations within the central 8° (p ≤ 0.005).

Conclusions :
Scotopic function is normal in iAMD eyes without RPD but is reduced in iAMD eyes with RPD, in the central 8°. These findings suggest that the abnormal rod function is likely driven by RPD rather than iAMD.

This is an abstract that was submitted for the 2017 ARVO Annual Meeting, held in Baltimore, MD, May 7-11, 2017.